Prosthetic devices that are delivered intraluminally, such as stents, valves, occluders, shunts, etc., are typically designed to be self expanding or balloon expandable such that they engage the walls of the vessel or duct to become permanently anchored there. To ensure that the prosthesis does not migrate after placement, anchoring barbs are often used that are configured to embed into adjacent tissue and hold the device in place. Barbs are an especially important component of endovascular stent grafts used to exclude an aneurysm sac formed in a blood vessel. For example, the high velocity of blood within the aorta makes it essential to securely anchor the prosthesis when treating an aortic abdominal aneurysm (AAA). Migration of the device downstream can result in the proximal seal of the aneurysm sac being compromised, which could be catastrophic in the event that the aneurysm sac ruptures. Barb fixation is method of fixation found in a variety of intraluminal prostheses, such as the ZENITH® Endovascular Stent Graft (Cook Incorporated), which relies on barb to anchor the proximal end of the device in the healthy portion of the aorta above the renal arteries.
In an intraluminal prosthesis formed from a wire frame or support structure, the barbs typically comprise separate elements attached to the frame at strategic points therealong by some method of attachment. Typically, short sections of wire or similar material are used which are soldered to a strut of the frame such that they extend outward for engaging tissue. In the body, solder is subject to corrosion when in contact with bodily fluids, so mechanical methods of attachment have been used as an additional measure to reduce the incidence of barb failure. U.S. Pat. No. 6,200,336 to Pavcnik discloses the use of short section of cannula to further secure the barb to the strut. U.S. Pat. No. 5,720,776 to Chuter et al. discloses the use of a helical coil at the base of the barb that encircles the strut to provide a mechanical attachment in addition to the solder bond. While standard methods such as these usually provide adequate fixation, barb failure due to fracture of the strut or weld is a relatively common phenomenon in situations where there are high repetitive mechanical stresses, often due in part to limitations of the barb design and the method of manufacture and/or attachment.
What is needed is a simplified barb design that is easy to manufacture, is readily and securely attachable to the prosthesis, and that produces predictable results with respect to fatigue life and anchoring ability to maintain the prosthesis at the site of deployment.